This proposal aims at a further analysis of the immune responses to antigens associated with bowel carcinomas in the rat with particular emphasis on embryonic antigens showing tissue-type specificity. A major goal is to develop techniques to further bolster those responses which have been found to lead to tumor rejection. The analysis will involve immunoprevention of bowel tumorigenesis and isograft rejection tests in vivo and further development of the techniques to induce and booster lymphocyte sensitization in vitro. The ultimate goal of these studies is to develop novel approaches to immunotherapy of bowel cancer. On the basis of recent demonstrations of humoral antibodies to antigens associated with bowel cancer cells appearing several months before detection of primary bowel lesions by X-ray or at laparotomy, sequential studies will be performed with several immune assays firmly established in our laboratory. The aims of these studies are 1) to define in great detail the immunological events during development of a primary bowel carcinoma by applying several assays for antibodies and antigens with various specificities, 2) to clarify the histopathological correlate to the initial appearance of antibodies to tumor associated antigens, and 3) to evaluate the feasability of utilizing some of the assays of specific immunity for diagnosis.